How to Grow Grey Oyster Mushrooms with a Grow Kit

Grow classic Grey Oyster mushrooms at home with a fully colonized ready-to-fruit block from Redwood Mushroom Supply. Grey Oyster is a forgiving, fast-growing variety with a mild savory flavor and substantial texture.

Keep the block inside its plastic grow bag and fruit through one clean side X or 3–4 inch slit. Grey Oyster performs best around 60–70°F with high humidity, indirect light, and plenty of fresh air.

Long stems with small caps usually mean the mushrooms need more fresh air—not more water. Avoid heavy direct misting on pins or mushroom clusters.

Grey Oyster, Growing Guides, Mushroom Grow Kit, Ready-to-Fruit Blocks

How to get started

Cut Open Grow Bag

Using a clean knife, cut one X or 3–4 inch side slit into one side of the bag—it’s okay to cut into the sawdust! You’ll likely see white, pink, or yellow growth inside, which is healthy mycelium. If you notice green fuzzy mold, reach out for support.

Spray Your Grow Bag

Fill the included sprayer with filtered or distilled water and lightly mist the exposed surface twice daily, or more often in dry conditions. Keep it damp without leaving water pooled in the opening. In a dry room, loosely cover the block with a clean, ventilated plastic bag and mist the inside of the cover.

Keep up this routine, and tiny mushrooms (“pins”) should appear in a few days. If not, you can loosely cover the block with a hole-punched bag to boost humidity.

Watch Your Mushrooms Grow

Once pins have started, keep the air around the cluster humid without soaking the young mushrooms directly. If using a humidity cover, mist its inside walls as needed and leave openings for fresh air

As your mushrooms grow, keep an eye out for signs that they’re ready to be harvested. Refer to our harvesting guide below for more information!

Harvest Your Mushrooms

Harvest when caps begin to flatten and edges start to curl upward. Grey Oysters are best when picked young—as they age, the flesh becomes tougher. Twist and pull entire clusters from the base, or cut with a clean knife. Don't leave stems behind as they can invite contamination.

After the first harvesting, remove any leftover stem tissue. Keep the block inside its plastic grow bag.

If the block feels dry and light, place it with the original cut facing down in clean, cool water for 12–18 hours. Drain thoroughly so no water remains in the bag. If the block does not feel dry, skip the soak.

Cover the original cut securely with clean tape, leaving the bag’s filter patch uncovered. Make one new X-shaped cut or 3–4-inch slit on the opposite broad side. Return the kit to humid conditions with plenty of fresh air. Mist lightly around the new cut or mist the inside of a loose humidity cover, following the earlier growing steps. A second flush may take another week or two and is often smaller than the first.

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FAQs and Tips

How long does it take for grey oyster mushrooms to grow?

Grey oyster mushrooms are among the fastest-growing varieties, usually producing their first harvest in 3-5 days after fruiting begins. You’ll start to see small pinheads form within the first week, and they’ll rapidly expand into full clusters just a few days later. Aim for approximately 60–70°F (16–21°C), with high humidity (85–95%) and good airflow to help the mushrooms develop their signature broad, curling caps.

Why are my oyster mushrooms growing long stems and small caps?

This is a common beginner issue caused by high CO₂ levels or low airflow. Grey oysters need plenty of fresh air exchange to form wide, healthy caps. If your mushrooms look leggy, open your fruiting chamber or tent more often, increase air circulation, or add a small fan nearby (not directly on your mushrooms) to keep air gently moving. Maintaining high humidity while improving airflow usually fixes the problem quickly.

Can I harvest more than once from my grow kit?

Yes — most oyster grow kits can produce 2–3 flushes of mushrooms. After the first harvesting, remove any leftover stem tissue. Keep the block inside its plastic grow bag.

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